This invention relates to a wear indicator for disc brakes. More particularly, it relates to a wear indicator for disc brakes of the type intended for heavy duty truck applications.
Lining wear can be readily checked in a drum type brake by either, as in passenger car applications, removing the wheel or, as in heavy duty truck applications, viewing the shoe thickness through a view port provided in the wheel expressly for that purpose. Lining wear in a disc brake passenger car application can be readily checked by removing the wheel. However, checking the lining wear in a disc brake heavy duty truck application is extremely difficult. Specifically, it is not feasible to use a viewing port as in the case of drum brakes since the disc brake pads, by virtue of their orientation, reveal their thickness only when viewed in a fore and aft direction, and viewing in this direction is blocked by the tire. And removing the wheel--or wheels--of a heavy duty truck is a time consuming and expensive task, requiring removal of the associated drive axle shaft, replacement of lost axle lubricant, and lifting of a tire/wheel mass weighing upwards of 400 pounds. Whereas various systems have been proposed for checking lining wear on a heavy duty truck disc brake application without removing the wheel assembly, the proposed systems have been complicated, expensive, or ineffective and, accordingly, none have met with any substantial degree of commercial success.